Prepare pint pickling jars per manufacturers directions.
Coarsely chop tomatoes and onions in batches in a food processor and reserve them.
Combine vinegar, sugar and salt in a stock pot, and bring to a boil over high heat. Add all vegetables and boil the mixture vigorously for 2 to 3 minutes.
Spoon the relish into prepared, hot jars, leaving 1/2 inch of headspace.
(Make sure to get some jalapeno slices in each jar).
Process the jars in a water bath canner for 10 minutes.